This invention relates to a beam deflector for use with a cathode ray tube.
Magnetic deflection is normally used in cathode ray tubes such as television picture tubes or the like having an electric gun provided to emit electrons toward a fluorescent screen. It is the common practice to deflect an electron beam in a cathode ray tube by a deflection yoke provided around the neck portion of the cathode ray tube. The deflection yoke has a coil portion wound to have a uniform thickness so as to produce a uniform magnetic field deflecting the electron beam in the cathode ray tube. The uniform magnetic field provides a good beam-focusing performance; however, it tends to cause picture distortion at and near the edges of the screen of the cathode ray tube. In order to correct the picture distortion, the deflection yoke has another coil portion wound to have a non-uniform thickness so as to produce a pincushion magnetic field for deflecting the electron beam in the cathode ray tube. However, the pincushion magnetic field tends to degrade the beam-focusing performance. Therefore, the conventional beam deflector cannot correct the picture distortion to a sufficient degree without the significant sacrifice of the beam-focusing performance.